(2)
SWPM 20-20-00, Electrical Bonding and Grounding
B. Equipment
(1) Bonding Meter (SWPM 20-20-00)
C. Procedure
CAUTION: YOU MUST PREPARE THE HF ANTENNA COUPLER(S) FOR REMOVAL. IF YOU DO NOT PREPARE FOR THE REMOVAL, YOU CAN EASILY CAUSE DAMAGE TO THE INTERNAL PARTS OF THE HF ANTENNA COUPLER(S).
(1)
Remove the HF antenna coupler(s) (AMM 23-11-61).
(2)
Make sure these circuit breakers are open and have DO-NOT-CLOSE tags attached:
WARNING: MAKE SURE THE ELECTRICAL POWER IS REMOVED FROM EACH HF COMMUNICATION SYSTEM. HF SIGNALS CAN CAUSE ELECTRICAL SHOCKS AND INJURY TO PERSONS.
(a) On the overhead circuit breaker panel, P7:
1) HF1
2) HF 2 (if installed)
(3)
Measure the resistance that follows at the antenna coupler(s) mount (SWPM 20-20-00):
(a)
The antenna coupler mount to the center conductor at the rear of the mount. 1) Make sure the resistance is 10 milliohms or less.
(b)
The front spar to the center conductor at the rear of the antenna coupler mount. 1) Make sure the resistance is 10 milliohms or less.
(4)
Install the HF antenna couplers (AMM 23-11-61).
504
Aug 01/94 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 23-11-61 Page 601
E03555
HF Antenna Bonding Check 503
23-11-61 Figure 601 Feb 20/94
Page 602
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
VHF COMMUNICATION SYSTEM - DESCRIPTION AND OPERATION
1. General
A. Two independent very high frequency (VHF) communication systems are installed on the airplane. The VHF systems provide amplitude modulated voice communication between aircraft and ground or other aircraft. Communication in the 118 to 135.975 MHz frequency range on any of 720 channels with a 25 kHz spacing may be accomplished. VHF control panels provide a means of selecting the desired operating frequency. Average communicating distances from the aircraft to ground are approximately 30 miles at 1000 feet and 135 miles at 10,000 feet.
B. Each VHF system is composed of one transceiver, control panel and antenna. The transceivers are installed in electronic equipment rack E2. VHF No. 1 and VHF No. 2 control panels are located on the aft section of the control stand in the control cabin. VHF No. 1 control panel is on the captain's side and VHF No. 2 control panel is on the first officer's side. VHF No. 1 antenna is at station 627, top centerline of the fuselage. VHF No. 2 antenna is at station 511, bottom centerline of the fuselage (Fig. 1).
C. The VHF systems use 28 volt dc power obtained from circuit breakers on load control centers P18 and P6. VHF No. 1 system power is obtained from the standby dc bus on circuit breaker panel P18-2. VHF No. 2 system power is obtained from switched electronics bus No. 2 on circuit breaker panel P6-1.
D. Communication on each VHF communication system is completed through the audio selector panels of the audio selecting system (Ref 23-53-0).
2. Control Panel
A. Two identical VHF control panels are installed in the control stand. On GJ ALL EXCEPT B-2509 thru B-2510, each panel contains VHF communication and VHF navigation systems controls; however, only those components relating to the VHF communication systems will be described.
5C8
Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 23-21-01 Page 1
K89296
VHF Communication System Component Location 5C8
23-21-01 Figure 1 Jun 20/85
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. On GJ B-2509 thru B-2510, VHF control panels consist of two frequency selection knobs, a transfer switch, and a test button. Rotation of the two outer knobs sets up the frequency which appears in a window above the knobs. The outermost knob has 18 positions numbered 118 thru 135. The next knob has 40 positions numbered 0.00 thru 0.975. (The 0.005 digit does not appear in the window.) Any of 720 channels with 25-kHz spacing may be selected. The transfer switch is used to select the right or left set of frequencies. Pressing the TEST button disables receiver squelch circuits. If background noise increases, the receiver is operating properly.
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